Electric motors & motor controls engineering | Forum profile

( Attached I have corrected errors in the 12 pole analysis. It still shows a phase unbalance on the 12 pole and now a slight magnitude unbalance also \(0.953 distribution factors for A and C phase, but 0.943 for B phase\). I don't rule out the fact there may be some remaining error in there - either typo or logical error.  But B phase was after all the one that looked different than the others. If you are bored, you are...

( I would investigate noise abatement techniques as well as having an oversized stator wound with an 1800RPM winding and a 1200 RPM winding. Called a two winding two speed motor when you need other than a 2:1 ratio. This is not to rule ut a VFD. I would investigate all three approaches and quite possibly one will be the clear best choice on comparison. , )

( Well done Ray. You explained it all much better than I ever could. Happy Holidays. , )

( Note that Bill's idea results in a slower motor than what was recommended. 45Hz equates to 1350 Srpm, something you can't get by changing the number of poles \(in other words, you can't wind 5.33 poles\). 1200RPM equates to 40Hz. Should have been said earlier; voltage control on an AC squirrel cage motor, be via it mag-amp, SCR or even connecting in Y, will produce lower TORQUE, but speed is based on frequency and the number...

BTW, I do plan to continue to examine this question further...after having christmas fun first!

Hi genman196 A picture or photo of the broken shaft is worth a 1000 words. Lots more info needed if you want a better answer. how long as the motor been in service? What was the torque load? What was the torque on the shaft? etc etc. desertfox

Quote: an installation where the electricians thought they were smarter than the engineers This could describe most of the projects I've worked on.

( Yes, you can. But if you do consider the following: Will the compressor manufacturer honour the warranty? Probably not. Will it break? Probably. It's your compressor; do what you want provided it remains compliant with the applicable codes, but the manufacturer usually sets these limits because they are safe for the machine.      , )

( No Mike.  NEC couldn't care less if an installation functions correctly or not.  They are there to prevent inconvenient fires and to a lessor extent electrocution. If the wire insulation values are adequate then they can share the conduit. , )

 Hi, Electricpete, Thanks for useful link (Reliance). You  wrote: I guess doing a full vector diagram provides better insight as to what is the degree of imbalance. That's true. Right way to know what is the degree of imbalance is doing a vector diagram to see how much  the angle of  mmf -vectors deviate from the ideal direction  and...